OFFSET
2,2
FORMULA
E.g.f.: A(x) = log(1 + x + x^2)^2 / 2!.
EXAMPLE
E.g.f.: A(x) = 1*x^2/2! + 3*x^3/3! - 13*x^4/4! - 10*x^5/5! + 394*x^6/6! +...
MATHEMATICA
With[{nn=30}, Drop[CoefficientList[Series[Log[1+x+x^2]^2/2, {x, 0, nn}], x] Range[ 0, nn]!, 2]] (* Harvey P. Dale, Feb 28 2013 *)
PROG
(PARI) a(n)=(n+2)!*polcoeff(log(1+x+x^2 +x*O(x^(n+2)))^2/2!, n+2)
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Jan 10 2008
STATUS
approved